Allergenic extracts cross linked under acid conditions with inorganic cyanates

ABSTRACT

Desensitizing or immunizing agents are provided for treating hypersensitive or allergic conditions. Modified allergenic material is prepared comprising an allergenic protein or glycoprotein crosslinked intermolecularly or intramolecularly with an inorganic cyanate. The modified material has reduced allergenicity relative to the uncrosslinked allergen and has the ability to produce antibodies having cross-specificity for the uncrosslinked allergenic protein or glycoprotein.

United States Patent Mullan et al.

ALLERGENIC EXTRACTS CROSS LINKED UNDER ACID CONDITIONS WITH INORGANIC CYANATES Inventors: Noel Austin Mullan; Brian George Overeil, both of Dorlcing, England Assignee: Beecham Group Limited, Great Britain Filed: July 20, 1973 Appl. No.: 381,342

Related US. Application Data Division of Ser. No. 59,745, July 30, 1970, Pat. No. 3,794,630.

Foreign Application Priority Data Aug. 6, 1969 United Kingdom 39289/69 May 15, 1970 United Kingdom 23621/70 May 16, 1970 United Kingdom 23853/70 US. Cl. 260/112 R; 424/91 Int. Cl C07g 7/00 Field of Search 260/1 12 R; 424/91 51 July a, 1975 [56] References Cited UNITED STATES PATENTS 2,816,099 12/1957 Young et al. 260/112 R X OTHER PUBLICATIONS Journal of Biological Chemistry, Vol. 238, 1963, pp. 214-226, Stark et al.

Chem. Abstracts, Vol. 70, 1967), 47862t, Stark.

1969 (effective date,

Primary Examinerl ioward E. Schain 16 Claims, N0 Drawings ALLERGENTQ EKTRATCTS CRUSS LTNKETD) UNDER A ClilD @UNDTTIUNS WTTll-ll TNUQGANT tCiKAhlATlES This is a divisional of ourcopending application Ser. No. 59,745, filed July 30, 1970, now US. Pat. No. 3,794,630.

The present invention relates to desensitizing or immunizing agents useful in the treatment of hypersensitive or allergic conditions, and to a method for their preparation.

it is well known that some individuals are allergic or hypersensitive to certain allergenic materials such as pollens, house dust, cat fur, cereals and a host of other common substances. Such individuals can suffer acute discomfort as a result of their allergic conditions which may manifest themselves in such diseases as asthma, hay fever, eczema, dermatitis and migraine. Consequently work continues to find suitable treatments which will alleviate the suffering of the allergic patient.

()ne technique which has been used in the past in the treatment of allergic conditions is the so-called desensitization therapy. The patient undergoing such therapy is administered repeated gradually increasing doses of an extract of the particular allergenic material or materials to which he is sensitive. At the end of a course of treatment the patients natural resistance to the allergen is usually greatly enhanced, presumably as a result of the build-up of antibodies in his body, stimulated by the administered extract.

As will be appreciated, this desensitization therapy suffers from certain disadvantages, not the least of which lies in the possibilities that a dangerously high dose of allergen may inadvertently be administered, resulting in a general anaphylactic reaction in the patient. lt has been suggested that this problem would be overcome if it were possible to modify the allergenic materials in such a way that their allergenicity is reduced relative to their desensitizing and/or immunizing properties. in other words, if the allergenic material could be rendered harmless, or at least less harmful to the sensitive patient, while at the time retaining its ability to stimulate antibody production, one of the main disadvantages of desensitization therapy could be removed.

According to the present invention there is provided a process for the preparation of a modified allergenic material, which process comprises the reaction of an allergenic material with a polyaldehyde, a polylretone, a carbodiimide, an epihalohydrin or an inorganic cyanate, with the proviso that when an inorganic cyanate is employed the reaction is carried out under acid con ditions.

The allergenic starting material which is modified according to the process of this invention may be obtained from an allergen-containing substance such as pollen by extracting the allergen-containing substance with a suitable solvent, usually aqueous, in a known manner. The allergenic extract obtained in this way consists principally of protein or glycoprotein, usually contaminated with free carbohydrate. The allergenic extract is then usually purified by removing some of the contaminants, e.g., by dialysis, precipitation or gel filtration, and the resulting purified allergenic material may then be treated according to the process of this invention. A fuller description of some of the techniques available can be found in an article by .i. N. Newell in the Journal of Allergy, Vol. 13, 1942, pages 177 to 203, particularly page 187. in another useful extraction procedure, the allergen-containing material or an aqueous extract thereof is treated with aqueous phenol and the allergenic extract is recovered from the phenol phase.

The polyaldehyde and polyketone reagents which lie within the scope of this invention include dialdehydes and diketones as well as the higher aldehydes and ketones. Generally of the polylretones and polyaldehydes which may be used we prefer to use dialdehydes, e.g., those having from 2 to about 24 carbon atoms in the molecule. The dialdehyde may be aliphatic, cycloaliphatic, heterocyclic or aromatic, and may have either a straight or branched chain structure, e.g., glyoxal, 1,3-propanedial, 1,4-butanedial, glutaraldehyde and 0:, ctr-dialdehydes having from 14 to 24 carbon atoms in the molecule. A. particularly preferred dialdehyde is glutaraldehyde.

The term carbodiimide as used in the present specification refers to compounds of formula (I) and salts thereof:

RN=C=I IR 1 wherein R and R are the same or different and each is an aliphatic, aromatic or heterocyclic radical. The preferred carbodiimides for use in the present invention are watersoluble, e.g., 1-cyclohexyl-3-(2- morpholinoethyl) carbodiimide metho-p-toluenesulphonate.

As used herein the term epihalohydrin refers to compounds of formula (II):

CH2CH2 Cll-ll X (ll) wherein X is a halogen atom, particularly bromine or chlorine. We find that good results are obtained with epichlorohydrin.

As examples of inorganic cyanate ion reagents may be mentioned the alkali metal cyanates, particularly potassium cyanate; and the alkaline earth metal cyanates.

As a general rule, allergenic proteins are fairly resistant to denaturation and can usually be heated to relatively high temperatures without denaturation taking place. The process of this invention can thus take place over a wide range of temperatures although in practice it will generally not be necessary or desirable to exceed a temperature of about C. When dialdehydes are employed it is preferred to operate at a temperature below 37C, and in practice we prefer to carry out the reaction at room temperature in each case, i.e., about 20 25C. When employing dialdehydes, extreme reaction conditions should be avoided in order to reduce undesirable byproducts such as are produced by self condensation of the aldehydes.

lln the case of polyaldehydes and polyketones, the pH at which the process of this invention should be carried out is not critical. A suitable pH range is from about 4 to about 8, with a pH of about 5 being preferred. Very low pH values should be avoided in order to reduce possible self condensation of the aldehydes.

Similarly in the case of epihalohydrin and carbodiimides, the reaction can be carried out at any convenient pll-ll, although we prefer to avoid extremes of pll-l. For the epihalohydrin the reaction proceeds smoothly at alkaline pll-ls, suitably at about plHl 8. lln the case of the carbodiimide, the reaction is preferably carried out at acid plhls, suitably at pH about 5.

The reaction of the allergenic protein withan inorganic cyanate reagent in the process of this invention must be carried out at acid pHs preferably at a pH of aboutv 5.

The reagents used in the process of this invention are believed to act as cross-linking agents for the allergenic material, forming interand/or intra-molecular links. Thus, although the allergenic starting materials are watersoluble, the modified allergenic products of the present invention are usually only sparingly soluble. The solubility of the modified allergenic materials appears to be dependent on the extent of cross-linking, which in turn may vary according to such factors as the nature and quantity of reagent used and the reaction conditions. We are not aware of any empirical method of determining in advance the solubility characteristics of the modified allergenic products and consequently the reaction variables necessary to obtain a product having the desired solubility must be determined by trial and error. This is a matter of routine, however, and should present little difficulty to those skilled in the art.

In another embodiment of this invention there is provided a pharmaceutical preparation comprising the modified allergenic material prepared by the process described above, and a parenterally acceptable carrier. Suitable carriers, include isotonic salt or bufier solutions, oily carriers and other materials well known in the art. If desired an adjuvant such as tyrosine, alumina, aluminium hydroxide or aluminium phosphate, may be included.

The modified allergenic material is generally administered by subcutaneous injection. Dosage rates will vary according to the allergic condition of the patient.

Generally, in preparing pharmaceutical compositions in accordance with this invention, the modified allergenic material should be one which has a reduced solubility relative to the starting material, but which is sufficiently soluble in vivo to provide the desired release characteristics. We find that one way of achieving this is to use a sparingly soluble modified allergen absorbed on alumina and like materials. The degree of solubility of the cross-linked allergenic material is modified by absorption onto the alumina and the optimum in vivo release characteristics can be achieved by routine extration of 10 mg/ml. was pricked into the skin of grass- -water to remove residual soluble material. It was finally suspended in phenol-saline solution for storage.

Test of Allergenicity The suspension of insolubilized pollen at a concensensitive allergic patients. At the same time the starting material and phenol-saline solution respectively were pricked into other areas of skin of the same patients. Weal areas were measured after 10 minutes, and are .expressed in Table l in sq. mm. It can be seen that insolubilized material at 200 times the concentration of starting material has barely one tenth of its allergenicity: the retained allergenicity is thus negligible when compared with that of the starting material.

Test of Immunogenicity The insolubilized material and the starting material respectively were emulsified in Freunds complete adjuvant to give concentrations of 1 mg/ml. Groups of guinea-pigs were injected subcutaneously with one or other of the emulsions (0.5 ml.). After 22 days the animals were clipped free of hair on the flanks and a series of intradermal injections (0.1 ml.) of a serial dilution of purified Cocksfoot'pollen extract was made into the clipped areas. A 5% solution of Pontamine Sky Blue (0.4 ml.) was immediately injected intravenously. After 20 minutes'weal diameters were measured, and are recorded in Table 2.

It can be seen that not only does the glutaraldehydetreated material produce antibody which reacts with the starting material, but it is a more efficient immu-. nizer than the starting material.

perimentation. TABLE I On parenteral administration to animals of the modified allergenic materials of this invention, it has been Patient No Insolubilized Purified phnob found that appreciable levels of circulating antibody Cocksfoot Cocksfoot Saline are formed, the antibody having cross-specificity for Pa g the unmodified allergenic material. The modified matemg/m Lg/m rials tested did not cause any anaphylactic reaction in 5 21 84 12 16 32 9 hypersensitive animals. i :2 57 23 51 4 EXAMPLE 1 v g Total 65 224 42 Preparation of Insoluble Allergen Derivative with gflgfi Glutaraldehyde phenol- A partially purified extract of Cocksfoot pollen, consalme' 176 TABLE II Quinea lmmunizing Weal diameter (mm.) for quantity of Cocksfoot I[311g Eraagenal) pollen extract injected intraderrnally ummg ber l00p.g lOng lJ-g 0.1;Lg 0.0l rg 0.001;.Lg

1 Purified 15 p 0 0 0 0 Cocksfoot 2 Pollen l6 0 0 0 0 0 Extract 3 l7 0 0 0 0 TABLE ll-Continued Guinea lmmunizing Weal diameter (mm.) for quantity of Cocksfoot Pig material pollen extract injected intradermally Num- (05 mg) ber lOOug lOug lug (llug 0.0l J.g 0.001 Jig 4 l6 O 0 (J O 5 Glutaraldel4 0 O O 0 O hyde- 6 treated l2 l0 9 0 O 0 Cocksfoot 7 Pollen l4 l3 l2 l2 l0 8 Extract 8 l6 l4 12 l l l() 8 9 l2 l0 0 O O 0 l0 l2 9 0 O 0 0 EXAMPLE 2 The results of the immunogenicity tests are recorded Preparation of Carbodiimide-Treated Allergen Fifty mg of material which had been extracted from mixed grass pollens, and which had been partially purified by treatment with aqueous phenol and subsequent precipitation of protein from the phenol phase, so as to remove much of the carbohydrate and low molecular weight material, was dissolved in 5 ml. of 0.5 M. borate buffer, pH 8.85. 5 ml of a 2% solution of l-cyclohexyl- 3-(2-rnorpholinoethyl) carbodiimide metho-p-toluenesulphonate was added slowly, and the solution was stirred at room temperature overnight. The precipitate which formed was then centrifuged off, washed three times with borate buffer, and suspended in phenol saline.

TEST OF ALLERGENlClTY A suspension of the test material and a solution of the starting material, both in phenol-saline, and the me dium itself, were respectively pricked into the skin of grass sensitive allergic patients. Weal areas were measured after 10 minutes.

The results of the allergenicity test are shown in Table III:

TABLE Ill Patient Mixed grass Carbodimide- Phenol No. pollen extract treated mixed saline 50 ug/ml grass pollen extract Total l 12 5 0 Figures indicate weal areas (sq.mm.).

TEST (NF KMMUNOGENICITY I blue-colored weals formed at some of the sites of intradermal injection, indicating the presence of antibody with specificity for the starting material. Weal diameters were measured and recorded.

in Table IV:

TABLE IV Guinea immunizing Weal diameter (MMs) for quantity Pig No. Material of mixed grass pollen extract 5 mg injected intradermally #g #2 Mg as #2 1 mixed l4 l2 l0 9 8 8 2 grass pol l4 l3 l0 9 8 3 len exl6 l4 l2 l0 9 9 4 tract l4 l3 l0 5 carbodiimidel4 12 IO l0 9 6 treated mixed l2 l0 7 grass pollen l2 l0 9 9 9 8 extract it can be seen from the results shown in Tables Ill and IV that higher levels of antibody were produced by immunization with the carbodiimide modified allergen, but that the allergenicity of the material was negligible.

EXAMPLE 3 50 mg of material which had been extracted from mixed grass pollens, and which had been partially purifled so as to remove much of the carbohydrate and low molecular weight material, was dissolved in 5 ml of 0.01 M phosphate buffer pH 8.0. 1 ml of l-chloro-Z: 3-epoxypropane was added slowly and the mixture was stirred overnight at room temperature. The precipitate which formed was centrifuged off, washed with phosphate buffer, and suspended in phenol saline.

TEST OF ALLERGENICITY A suspension of the test material and a solution of the starting material, both in phenol-saline, and the medium itself, were respectively pricked into the skin of grass sensitive allergic patients. Weal areas were measured after 10 minutes. The results of the test of allergenicity are shown in Table V:

Figures indicate weal areas (sq.mm.).

TEST OF HMMUNOGENTCHTY Replicate guinea pigs were immunized by subcutaneous injection of an emulsion containing the test mate- 7 rial in Freunds complete adjuvant. A similar set of guinea pigs were immunized with the unmodified starting material adjuvanted in the same way. After 21-8 TABLE VIII Allergenicity of Epibromohydrin-Treated Allergen Patient Cocksfoot extract Epibromohydrin-treated Phenol days the animals were cllpped free of hair on the flanks v No I [lg/ml Cocksfoot pone" Saline and a series of mtradermal in ections (O.l ml) of a seemam 00 Lg/ml rial dilution of starting material terminating with normal saline was made into the clipped area. 8 8 A 5% solution of Pontamine Blue Sky (0.4 ml) was 3 22 0 0 immediately injected intravenously. After minutes 1 4 0 0 blue-colored weals formed at some of the sites of intra- 0 Tom] 70 0 dermal injection, indicating the presence of antibody with specificity for the starting material. Weal diame- EXAMPLE 5 ters were measured and recorded. The results of the PREPARATION OF CYANATE MODIFIED test of immunogenicity are shown in Table VI: ALLERGEN TABLE VI Weal diameter (mms) for quantity of mixed Guinea lmmunizing grass pollen extract injected i.d. Pig No. material I00 pg 10 pg 1 pg O.l pg 0.01 pg 0.001 pg 1 mixed grass l4 l3 l0 2 pollen exl6 l4 l2 l0 9 9 3 tract l4 l3 l0 9 8 4 (5 mg) 14 12 IO 9 8 8 5 Epichlorhyl 2 l0 6 drin-treated l0 7 mixed grass 8 pollen ex- 10 tract (5 mg) 9 mixed grass 12 9 l0 pollen exl4 l2 9 ll tract 12 ll 9 12 (0.5 mg) 14 12 9 l 3 Epichlorhyl0 8 l4 drin-treated l5 grass pollen l0 8 l6 extract (0.5 mg) g It can be seen from the above results that detectable levels of antibody were produced by immunization with epichlorhydrin-treated allergens while the allergenicity was reduced to a negligible level.

EXAMPLE 4 Results of the biological testing are shown in Tables III and IV. The testing procedures were identical with those of Example 3. Detectable levels of antibody were produced by immunization, while allergenicity was reduced to negligible levels.

TABLE VII An aqueous extract of mixed grass pollens (Bent, Broom, Cocksfoot, Dogstail, False Oat, Fescue, Foxtail, Meadow Rye, Timothy Vernal and Yorkshire Fog) was partially purified by treatment with aqueous phenol followed by precipitation of protein from the phenol phase to remove much of the carbohydrate and the low molecular weight materials. 50 mg of the resultant partially purified allergenic protein was dissolved in 5 ml of water and the pH adjusted to pH 8 by the addition of sodium hydroxide solution. The pH was then further adjusted 5.0 with acetic acid, 0.2 g of potassium cyanate was added, and the mixture stirred at room temperature overnight. The precipitate which formed was washed repeatedly with phosphate buffer at pH 8 and then suspended in phenol saline.

TEST OF ALLERGENICITY A suspension of the cyanate-modified allergen prepared as above, a suspension of the unmodified par- Immunogenicity of Epibromohydrin-Treated Allergen bluecolored weals formed and some of the sites of intradermal injection, indicating the presence of antibody with specificity for the starting material. Again weal diameters were measured and are recorded in Table X. It can be seen that the cyanate modified allergen retains the immunizing specificity of the starting material.

TABLE X Weal diameter (mms) for quantity of mixed Guinea immunizing grass pollen extract injected i.d. Pig. No. material lOO,u.g lp.g Lug O 1 ug 0.0Ip.g 0.00lp.g

1 Mixed grass l4 l2 l0 9 8 8 2 pollen extract l4 l3 l0 9 8 3 (5 mg) I6 l4 12 IO 9 9 4 l4 l3 5 Cyanate-treated l2 9 7 (7 mixed grass 12 9 7 7 pollen extract l0 8 (5 mg) 12 9 Mixed grass 14 12 9 10 pollen extract 12 ll 9 1 l 0.5 mg) 14 12 9 l2 I2 9 TABLE IX EXAMPLE 6 Mixed grass cyallate'treated pheflol In order to obtain confirmation of the biological test- Patient No. pollen extract mixed grass saline 50 ,ig/mi pollen extract mg results the procedure of Example 5 was repeated.

1 mg/ml The results of the test of the allergenicity of the modi- I 12 4 0 3O fied allergen are recorded in Table XI and the results 2 3 2 0 of the tests of the immunogenicity of the cyanate- Z g 8 modified allergen are recorded in Table XII. 5 I5 5 O 6 62 24 O Total 1 I2 44 0 TEST OF IMMUNOGENICITY Replicate guinea pigs were immunized by subcutaneous injection of an emulsion containing the cyanate- 4O modified allergen in Freunds complete adjuvant. A similar set of guinea pigs were immunized with the unmodified starting material adjuvanted in the same way. After 21-28 days both sets of animals were clipped free of hair on the flanks and a series of intradermal injec- 4 tions (0.1 ml) of a serial solution of the starting material terminating with normal saline was made into the clipped area.

A 5% solution of Pontamine skyblue (0.4 ml) was immediately injected intravenously. After 20 minutes TABLE XI Mixed grass Cyanatetreated Patient pollen extract mixed grass Phenol No. pg/ml pollen extract saline 2 mg/ml Total 50 1 1 Figures indicate weal areas (sq.mm.).

TABLE XII Weal diameter (mms) for quantity of mixed Guinea Immunizing grass pollen extract injected id. Pig No. material IOOpLg l0,u.g lptg O.l .Lg 0.01;.tg 0.00Ip.g

1 Mixed grass l2 l0 9 8 2 pollen extract I2 10 7 3 (5 mg) 12 1O 8 4 12 1O 9 5 Cyanatetreated l2 IO 6 mixed grass 12 9 7 pollen extract l4 l2 9 8 (5 mg) l4 l0 9 Mixed grass l4 l0 l0 pollen extract 12 l 1 9 l l (0.5 mg) 10 9 l2 l3 Cyanate-treated 12 l l 8 14 mixed grass 12 l5 pollen extract 10 l6 (0.5 mg) 11 EXAMPLE 7 TREATMENT OF POLLEN EXTRACT WITI-I PI-IENYL GLYOXAL METHOD the unrn odifiedf'starting material adjuvanted in the i sameway. ;A;fte'r 2 8 daysf'both sets' of animals were clippedjfree. of hairJ'on the flanks and a series of intraderrnal injections "(0.1 ml) of a serial solution of the starting material terminating with normal saline was made into the clipped area. A 5% solution of Pontamine sky blue- 0.4' ml) was immediatelyinjected intravenously. After-'20 minutes blue colored weals formed 7 at some of the sites of intradermal injection, indicating the presence of antibody with specificity for the starting material. Weal areas were measured and are recorded in Table XIV.

TABLE XIV Guinea Pig Immunizing Weal diameter (mm) for quantity of Cocksfoot pollen extract injected i.d.

No. Material lp.g IOug lug 0. lug 0.0 l p.g 0.00lp.g

l Cocksfoot l4 l4 l0 l0 9 7 2 pollen l4 l2 8 7 6 3 extract 12 ll 10 9 7 4 mg) 12 I 1 9 9 8 l Phenylglyoxal l2 1 l 2 treated cocks- I3 3 foot pollen l2 4 extract(0.5mg) a pended in phenol saline TABLE XV TEST OF ALLERGENICITY I Patient Cocksfoot pollen Nitromdanedione Phenol A suspension of the phenylglyoxal-modified material extract treated ex ract saline prepared as above, a suspension of the unmodified phe- 3o 50 Lg/m] 1 mg/m' nol treated Cocksfoot extract (both in phenol-saline) 1 3 0 0 and the phenol-saline medium itself were respectively 3 g l pricked into the skin of grass-sensitive allergic patients. 4 5 I 8 Weal areas were measured after ten minutes and are expressed in Table XIII in sq.mm. Tmal 27 5 1 TABLE XIII Patient Cocksfoot pollen Phenylglyoxyal-treated Phenol TEST OF IMMUNOGENICITY No. extract extract Saline 50 /ml 1 mg/m] 40 Replicate guinea pigs were immunised by subcutaneous injection of an emulsion containing the nitroin- I 35 0 0 d 2 27 4 O Y anedlone modified material in Freud s complete ad u- 3 19 2 l vant. A similar set of guinea pigs were immunised with Total 91 6 l the unmodified starting material adjuvanted in the same way. After 28 days, bothsets of animals were clipped free of hair on the flanks and a series of intradermal injections (0.1 ml) of a serial solution of the TEST OF IMMUNOGENICITY starting material terminating with normal saline was Replicate guinea pigs were immunized by subcutanemade into the clipped area. A 5% solution of Pontaous injection of an emulsion containing the phenylglyoxal modified material in Freunds complete adjuvant. A similar set of guinea pigs were immunized with mine sky blue (0.4 ml) was immediately injected intraand recorded in Table XVI.

TABLE XVI Weal diameter (mm) for quantity of cocksfoot EXAMPLE 8 TREATMENT OF POLLEN EXTRACT WITI-I GLUTARALDEHYDE AND SUBSEQUENT ABSORPTION INTO ALUMINIUM HYDROXIDE METHOD 1 ml of of glutaraldehyde solution was added to 9ml of an aqueous extract of timothy pollen containing l mg/ml at pH 5.3. The mixture was stirred at room temperature for 3 days. 6 ml of 2% aluminium hydroxide solution were added and the mixture stirred for one hour. After centrifugation the precipitate was washed twice in 0.01 M phosphate buffer pH 8 and three times in distilled water and finally resuspended to a concentration of 1 mg/ml pollen in phenol saline. The procedure was repeated without the addition of glutaraldehyde, the final suspension serving as a control in the immunizing specificity test.

TEST OF IMMUNIZING SPECIFICITY Replicate guinea pigs were immunized by subcutaneous injection of the alumina-glutaraldehyde adsorbed modified material. A similar set of guinea pigs were immunized with unmodified alumina-adsorbed timothy pollen extract at a pollen concentration of l mg/rnl. 21 days later a repeat injection was given and the animals bled 10 days later.

Passive cutaneous anaphylaxis was carried out on the sera by injection of serial dilutions intradermally into a clipped area on the flanks of a set of guinea pigs. The pigs were then challenged intravenously with the unmodified aqueous timothy extract, containing 0.4 ml Pontamine sky blue solution, five hours later. Results obtained with different concentrations of challenging antigen are shown in Table XVIII for the modified material and Table XIX for the control suspension without glutaraldehyde.

TABLE XVI Challenge Guinea Pig Freeze-dried aqueous Weal diameters in mm at serum No. Timothy pollen extract dilution of l 1 mg/ml 22 2O l6 l0 2 100 #g/ml 2O l7 l3 3 l0 ug/ml 18 4 5 .Lg/ml l4 TABLE XVII Challenge Guinea Pig Freeze-dried aqueous Weal diameters in mm at serum No. Timothy pollen extract dilution of 5 125 625 3125 Same 5 1 mg/ml 25 16 6 100 pig/ml 2O l8 l6 7 l0 rg/ml 8 5 ug/ml TEST OF ALLERGENICITY A suspension of the above material, a solution of the unmodified pollen extract (both in phenol-saline) and the phenol saline medium itself were respectively pricked into the skin of grass-sensitive allergic patients. Weal areas were measured after 10 minutes and are expressed in Table XVII in sq.mm.

It can be seen that treatment with glutaraldehyde leads to enhanced antibody formation when compared with that from untreated material, although allergenic activity was reduced.

We claim:

I. A process for the preparation of a modified allergenic material which comprises an allergenic extract of pollen or house dust which consists principally of a protein or glycoprotein, which allergenic extract is crosslinked under acidic conditions interor intramolecularly with an inorganic cyanate, said modified allergenic material being substantially water-insoluble or only sparingly water-soluble and having a reduced allergenicity relative to the uncrosslinked protein or glycoprotein and having the ability to stimulate the production of antibodies having cross-specificity for the unlinked protein or glycoprotein, which comprises reacting an allergenic extract of a pollen extract selected from the group consisting of Cocksfoot pollen, mixed grass pollens and timothy pollen or house dust with an inorganic cyanate at an acidic pH to reduce the allergenicity and recovering the modified allergenic material so produced.

2. A process according to claim 1 wherein the tern perature is below 100 C. Y 3. A process according to claim 1 wherein the pH is about 5.

4. A process according to claim 2 wherein the te'm perature is about room temperature. I

5. A process according to claim 1 wherein the inorganic cyanate is an alkali metal'cyanate or an alkaline earth metal cyanate.

6. A process according to claim 1 wherein the inorganic cyanate is potassium cyanate.

7. A process according to claim 1 wherein the allergenic extract is a pollen extract.

8. A process according to claim 1 wherein the allergenic extract is 'a house dust extract.

9. A modified allergenic material which comprises an allergenic extract of pollen or house dust which consists principally of a protein or glycoprotein, which allergenic extract is crosslinked under acidic conditions interor intramolecularly with an inorganic cyanate,

said modified allergenic material being substantially water-insoluble or only sparingly water' soluble and having a reduced allergenicity relative to the uncrosslinked protein or glycoprotein and having the ability to stimulate the production of antibodies having crossspecificity for the unlinked protein or glycoprotein.

10. A modified allergenic material according to claim 9 wherein the allergenic extract is a pollen extract. 1 I. A modified allergenic material according to claim 9 wherein the allergenic extract is a house dust extract.

12. A modified allergenic material according to claim 9 wherein the inorganic cyanate is an alkali metal cyanate or an alkaline earth metal cyanate. I

13. A modified allergenic material according to claim 9 wherein the inorganic cyanate is potassium cyanate.

14. A modified allergenic material according to claim 10 wherein the pollen is Cocksfoot pollen.

15. A modified allergenic material according to claim 10 wherein the pollen is mixed grass pollens.

16. A modified allergenic material according to claim 10 wherein the pollen is timothy pollen. 

1. A PROCESS FOR THE PREPARATION OF A MODIFIED ALLERGENIC MATERIAL WHICH COMPRISES AN ALLERGENIC EXTRACT TO POLLEN OR HOUSE DUST WHICH CONSISTS PRINCIPALLY OF A PROTEIN OR GLYCOPROTEIN, WHICH ALLERGENIC EXTRACT IS CROSSLINKED UNDER ACIDIC CONDITIONS INTER- OR INTRA-MOLECULARLY WITH AN INORGANIC CYANATE, SAID MODIFIED ALLERGENIC MATERIAL BEING SUBSTANTIALLY WATERINSOLUBLE OR ONLY SPARINGLY WATER-SOLUBLE AND HAVING A REDUCED ALLERGENICITY RELATIVE TO THE UNCROSSLINKED PROTEIN OR GLYCOPROTEIN AND HAVING THE ABILITY TO STIMULATE THE PRODUCTION OF ANTIBODIES HAVING CROSS-SPECIFICIY FOR THE UNLINDED PROTEIN OR GLYCOPROTEIN, WHICH COMPRISES REACTING AN ALLERGENIC EXTRACT OF A POLLEN EXTRACT SELECTED FROM THE GROUP CONSISTING OF COCKSFOOT POLLEN, MIXED GROSS POLLENS AND TIMOTHY POLLEN OR HOUSE DUST WITH AN INORGANIC CYANATE AT AN ACIDIC PH TO REDUCE THE ALLERGENICITY AND RECOVERING THE MODIFIED ALLERGENIC MATERIAL SO PRODUCED.
 2. A process according to claim 1 wherein the temperature is below 100* C.
 3. A process according to claim 1 wherein the pH is about
 5. 4. A process according to claim 2 wherein the temperature is about room temperature.
 5. A process according to claim 1 wherein the inorganic cyanate is an alkali metal cyanate or an alkaline earth metal cyanate.
 6. A process according to claim 1 wherein the inorganic cyanate is potassium cyanate.
 7. A process according to claim 1 wherein the allergenic extract is a pollen extract.
 8. A process according to claim 1 wherein the allergenic extract is a house dust extract.
 9. A modified allergenic material which comprises an allergenic extract of pollen or house dust which consists principally of a protein or glycoprotein, which allergenic extract is crosslinked under acidic conditions inter- or intramolecularly with an inorganic cyanate, said modified allergenic material being substantially water-insoluble or only sparingly water-soluble and having a reduced allergenicity relative to the uncrosslinked protein or glycoprotein and having the ability to stimulate the production of antibodies having cross-specificity for the unlinked protein or glycoprotein.
 10. A modified allergenic material according to claim 9 wherein the allergenic extract is a pollen extract.
 11. A modified allergenic material according to claim 9 wherein the allergenic extract is a house dust extract.
 12. A modified allergenic material according to claim 9 wherein the inorganic cyanate is an alkali metal cyanate or an alkaline earth metal cyanate.
 13. A modified allergenic material according to claim 9 wherein the inorganic cyanate is potassium cyanate.
 14. A modified allergenic material according to claim 10 wherein the pollen is Cocksfoot pollen.
 15. A modified allergenic material according to claim 10 wherein the pollen is mixed grass pollens.
 16. A modified allergenic material according to claim 10 wherein the pollen is timothy polLen. 